Troubleshooting (LTE-Advanced)
This topic contains information to help you troubleshoot measurements when using LTE Demodulation. You should also review Setting up an LTE-Advanced Measurement for additional measurement information.
PROBLEM |
POSSIBLE CAUSE |
SOLUTION |
---|---|---|
|
Signal not present. |
Check test setup connections. |
|
Component carrier too far from center frequency specified by Freq. Offset. |
Enable extended frequency lock range and adjust component carrier frequency offset to within ± 37.5 KHz of the LTE carrier frequency. |
|
Input is over-loaded or under ranged. |
Adjust input range. |
|
Frequency span is too narrow. |
Increase frequency span. |
|
Downlink: Incorrect Cell ID, RS-PRS, or CP Length
Uplink: Incorrect Half-subcarrier Shift, CP Length, or sync slot settings/user allocations. |
Make sure that the LTE-Advanced demodulator settings and user allocations match the input signal. |
|
I and Q channels are swapped. |
Enable the Mirror Freq. Spectrum setting. |
|
Component carrier has an incorrect P-SS. |
|
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Component carrier has incorrect symbol clock. |
Adjust Time Scale Factor to match the signal. |
|
I/Q misaligned using I+jQ receiver. |
Ensure that trigger delays for the hardware channels assigned to I and Q are correct. |
|
Component carrier contains an antenna port transmission with a phase rotation of more than 45 degrees and RS-PRS is set to . |
Set RS-PRS to to allow RS-PRS to be determined by Cell ID according to the standard. |
|
Both uplink and downlink transmissions present in a TDD component carrier being analyzed. |
Select Uplink Present in Signal or Downlink Present in Signal, as appropriate. |
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|
High EVM |
Time capture includes data where no LTE-Advanced signal is being transmitted. |
Make sure that the entire time capture is filled with an LTE-Advanced signal. The demodulator uses all of the time capture data (see Result Length) to calculate equalization coefficients. |
|
PDSCH parameters not configured correctly for a multi-antenna signal. |
Make sure that the precoding type, number of layers, number of codewords, CDD, and codebook index are set correctly for each user in the LTE Allocation Editor. |
|
Codeword 1 is being transmitted but is not included in analysis. |
Make sure the check box to the left of PDSCH tab is selected for user mappings that contain CW1 transmissions. in the |
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|
Only P-SS and S-SS have high EVM |
P-SS/S-SS Antenna Port is not set correctly. |
Make sure the P-SS/S-SS Antenna Port parameter is correct for the component carrier being analyzed. The port that P-SS and S-SS are transmitted on needs to be specified because the standard states that the receiver shall not make any assumptions about which antenna port P-SS and S-SS are transmitted on. |
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The display driver is not functioning correctly. |
Contact your PC manufacturer to see if a newer version of the display driver is available. If not, try decreasing the hardware acceleration. See the Windows documentation for instructions. |
See Also
About Opts BHG and BHH: LTE-Advanced Modulation Analysis
Setting up an LTE-Advanced Measurement